System and method for ankle arthroplasty

Abstract

A monolithic interpositional arthroplasty implant for use in repairing gyngylmus joints such as the joints of the ankle. The implant is a monolithic tibiotalar implant having a first major surface shaped to be positioned against a tibia. The tibia is allowed to articulate across the first major surface. A second major surface is shaped to be positioned against the talus.

What is claimed is: 
     
       1. A monolithic tibiotalar implant for use in arthroplasty repair of ginglymus joints, comprising: a first major surface of the monolithic implant curved for positioning against a tibia and configured to allow the tibia to articulate across the first major surface; a second major surface of the monolithic implant curved for positioning against a talus; and a protrusion proximate to the implant's anterior side sized to engage the neck of the talus, wherein the first and second major surfaces curve only in an anterior-posterior direction, and wherein the first major surface is curved differently than the second major surface such that the first major surface is adapted to be congruent with the tibia and the second major surface is adapted to be congruent with the talus, and wherein the monolithic implant is comprised of a polymeric biomaterial that includes both hard and soft segments to provide at least one of desirable wear resistance, congruency, and cushioning properties. 
     
     
       2. The implant according to  claim 1  wherein the monolithic tibiotalar implant has one or more external structures adapted to improve retention of the implant within the joint site. 
     
     
       3. The implant according to  claim 2  wherein the protrusion is located on the implant's anterior side. 
     
     
       4. The implant according to  claim 1  wherein the implant is comprised of a biomaterial. 
     
     
       5. The implant according to  claim 4  wherein the biomaterial is a polyurethane. 
     
     
       6. The implant according to  claim 5  wherein the polyurethane is biocompatible with respect to cytotoxicity, sensitization, genotoxicity, chronic toxicity, and carcinogenicity. 
     
     
       7. The implant according to  claim 5  wherein the polyurethane has a Shore hardness of at least about 60 D or less. 
     
     
       8. A method of repairing a tibiotalar joint, comprising the steps of providing and implanting an implant according to  claim 1 , the implant being inserted through an incision anterior to the tibiotalar joint. 
     
     
       9. The implant according to  claim 1  inserted into a ginglymus joint, the ginglymus joint being a tibiotalar joint, the monolithic implant's first major surface positioned against the tibia, its second major surface positioned against the talus, and the protrusion proximate the implant's anterior side is engaged with a neck of the talus. 
     
     
       10. The implant according to  claim 1 , wherein the implant is made of polyurethane having hard and soft segments. 
     
     
       11. The implant according to  claim 10 , wherein the hard segments are made of oligourethane units formed from diisocyanate and chain extender, and wherein the soft segments are made of polyol units. 
     
     
       12. A monolithic device for implantation into an ankle joint space within the body of a mammal, the device comprising:
 a monolithic structure fabricated from a biocompatible, biodurable material that is configured to be inserted into the joint compartment, the monolithic structure including first and second major surfaces, the first major surface curved for positioning against a tibia, such that the tibia can articulate across the first major surface, and the second major surface curved for positioning against a talus, wherein the monolithic device is substantially free of anchoring portions that need to be attached to the bone, cartilage, ligaments or other tissue, wherein the first and second major surfaces curve only in an anterior-posterior direction, and wherein the first major surface is curved differently than the second major surface such that the first major surface is adapted to be congruent with the tibia and the second major surface is adapted to be congruent with the talus, and wherein the monolithic implant is comprised of a polymeric biomaterial that includes both hard and soft segments to provide at least one of desirable wear resistance, congruency, and cushioning properties. 
 
     
     
       13. The device according to  claim 12  wherein stability of the device within the joint space is provided by the congruency of the device to the talus. 
     
     
       14. The device according to  claim 12 , wherein the monolithic structure is made of polyurethane having hard and soft segments. 
     
     
       15. The device according to  claim 14 , wherein the hard segments are made of oligourethane units formed from diisocyanate and chain extender, and the soft segments are made of polyol units. 
     
     
       16. A monolithic interpositional tibiotalar implant for use in repairing joints of the ankle, comprising:
 a first major surface curved for positioning against a tibia and curved to allow the tibia to articulate across the first major surface; and 
 a second major surface curved for positioning against a talus, wherein the implant has a protrusion proximate its anterior side configured to engage the neck of a talus to improve fixation to the talus, 
 wherein the monolithic implant is comprised of a polymeric biomaterial that includes both hard and soft segments to provide at least one of desirable wear resistance, congruency, and cushioning properties, and 
 wherein the first and second major surfaces curve only in an anterior-posterior direction. 
 
     
     
       17. The implant according to  claim 16 , wherein the hard segments are made of oligourethane units formed from diisocyanate and chain extender, and wherein the soft segments are made of polyol units.